Message Authenticator Generation Using Extended Hash Segmentation
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Solution Overview
Problem
Existing message authentication algorithms, such as CMAC, have a limited value of q1, which necessitates frequent updating of secret keys, increasing costs and reducing security due to dependence on the number of block cipher invocations.
Innovation Solution
A message authenticator generation apparatus that uses a hash function with an output length longer than the block size, combined with two or more block ciphers, to generate a message authenticator, reducing collisions and increasing randomness, thereby increasing the value of q1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a message authentication algorithm uses a block cipher with a limited block size, then the algorithm structure is simple, but the value of q1 is limited and key updates must be performed frequently
Solution Approach 1:
The hash function output is segmented into two separate values (first hash value and second hash value), each processed independently through block ciphers. This segmentation allows the system to achieve higher security (larger q1) by combining multiple block cipher operations on divided data, rather than processing the entire hash output through a single block cipher instance.
Solution Approach 2:
The patent implements nested block cipher operations where multiple block cipher encryptions are applied in sequence to different segments of the hash output. The first block cipher processes the first hash value, and the second block cipher processes the second hash value, creating a nested structure that amplifies security without requiring a larger fundamental block size.
2Reliability
If the number of block cipher invocations L is increased to improve security, then the value of q1 decreases, but if L is decreased then security is weakened
Solution Approach 1:
The patent changes the parameter of hash function output length from the standard block size to twice the block size (2n bits). This parameter change allows the system to divide the output into two n-bit segments, each processed by block ciphers, effectively doubling the security margin (q1) without increasing the number of block cipher invocations beyond what is already required for standard operations.
3Productivity
If a hash function with output length equal to block size is used, then the algorithm is efficient, but collisions occur more frequently reducing the value of q1
Solution Approach 1:
The patent extends the hash function output dimension from n bits to 2n bits, creating an additional dimension of security space. By dividing this extended output into two separate n-bit values and processing them through block ciphers, the system achieves collision resistance equivalent to O(2n) operations rather than O(2n/2), effectively doubling the security margin while maintaining processing efficiency.
Data Source
AI summary
A message authenticator generation apparatus (10) generates a message authenticator using a block cipher E having a block size n. A hash function unit (21) calculates a hash value w with a hash function h having an output length longer than n bits, taking as input a message M. A post-processing unit (22) performs calculations using the block cipher E on the hash value w calculated by the hash function unit (21), so as to calculate a message authenticator T not larger than the block size n for the message M.